Present day practice in crop harvesting utilizes the formation of bales of crop material such as hay or the like into stacks for storage by the employment of an automatic bale wagon. One type of bale wagon for use in this manner which has achieved wide spread commercial acceptance is the automatic bale wagon which employs the three table concept as originally illustrated and described in U.S. Pat. No. 2,848,172 issued to Gordan E. Grey.
The Grey bale wagon includes a first table which receives bales from a bale loader or pick up device on the wagon and accumulates a predetermined number of these bales, for example two, being arranged end-to-end in a row; a second table which successively receives the accumulated rows of bales from the first table and accumulates a plurality of such rows, such as four, five, or six rows, which plurality of rows is commonly called a tier of bales, and a third table or load bed which successively receives the tiers from the second table and accumulates a plurality of the tiers, for example, seven, to form a stack thereon. Once the stack has been accumulated on the load bed, it may be unloaded by pivoting the load bed approximately 90.degree. and depositing the stack on the ground or the like with the first tier of bales which was previously accumulated on the second table now being the lowermost tier of the stack in contact with the ground surface.
The Grey bale wagon deposited all of the bales in such a manner that tiers were formed with all bales laying on their edge sides so that the bales forming the lowermost tier are oriented such that a none-twine or -wire bearing side of each bale, commonly referred to as an "edge" of the bale, is in contact with the ground in order to avoid wire rusting or twine rotting which eventually would result in broken bales in the lowermost tier and would probably cause topling of the stack.
In order to enhance stability of the stack, it is desirable to provide one or more tie tiers within the stack, such being tiers have individual bales arranged to overlap two bales in adjacent tiers above and below the tier. Formation of one or more of such tie tiers can be accomplished during formation of the stack on the bale wagon, for example, through utilization of a mechanism which is similar to that illustrated and described in U.S. Pat. No. 3,395,814, which has been incorporated into several present day commercial models of the Grey bale wagon.
U.S. Pat. Nos. 3,945,507 to James A. Olson et al and 3,927,771 to Lee D. Butler et al relate to improved bale wagons for facilitating the formation of a block or tied tier type stack on the wagon, and particularly, these improvements facilitate tier pattern selection and formation on the wagon as well as formation of bales into a predetermined sequence of tier patterns to form a block.
In each of the Olson et al and Butler et al patents, a control mechanism is provided wherein the bales which are picked up from the field are initially placed on the first table of the wagon and are then deposited either "on edge" or "on flat" onto the second table according to the preselected tier pattern. The particular tier pattern is formed on the second table as successive bales are deposited thereon either singly or in pairs to form tie tiers, edge tiers or flat tiers as necessary. When the complete tier has been formed on the second table, the second table, along with the formed tier, is tilted to an upright position at which time the tier is deposited onto the third table or load bed of the wagon.
The third table is provided with a "rolling rack" against which the tiers rest after they have been deposited onto the third table. The rolling rack is provided with a hydraulic cylinder which initially moves the rack to its fully forward position at which time it is ready to receive the first tier.
As the second tier of bales is deposited onto the third table, it is necessary for the rolling rack to move rearwardly slightly to accommodate the second tier. To accomplish this in the past, the hydraulic circuit for the rolling rack cylinder was provided with a pressure relief valve which may be adjusted to the desired pressure. As the second table is hydraulically raised, the second tier pushes against the first tier which in turn pushes against the rolling rack to force the same rearwardly a distance approximately equal to the thickness of one tier while the associated hydraulic cylinder retracts a distance equal to about one-half of the tier thickness. As the pressure builds up in the hydraulic cylinder and associated hydraulic lines, the pressure relief valve opens releasing the fluid and permitting the rolling rack to retract along the third table until the second table is in its full upright position at which time no further force is exerted against the rolling tack, and the pressure relief valve recloses and movement of the rolling rack stops. At this time, the second table is lowered to begin receiving more bales and forming an additional tier, after which the foregoing operation is repeated.
The use of this pressure relief valve to control the movement of the rolling rack, has proved to be disadvantageous under some certain circumstances, however. Firstly, a very precise control of the pressure relief valve is necessary. If the setting were too high, excess pressure would build up in the hydraulic system which could damage various components of the bale wagon or cause the apparatus to jam. If the pressure relief valve setting were too low, the weight of the bales against the rolling rack, particularly during movement through the field, could cause the rack to slowly retract at an improper time. Further, if four or five tiers of bales are already on the third table, greater force is necessary from the second table in order to build up the pressure sufficient to open the relief valve.